Abstracts

Brain stimulation is evolving as treatment for intractable, localization related epilepsy. The most effective stimulation parameters and targets remain unknown. Treatment options for generalized epileptic encephalopathies are limited., An 18 yo woman with epileptic encephalopathy was implanted with a DBS (Medtronic) in the anterior nucleus of the thalamus (ANT) after failing to respond to all available AEDs, ketogenic diet and VNS. An ictal SPECT had demonstrated hyperperfusion in the thalamus. EEG with various stimulation parameters was quantified. Clinical outcome and serial EEG data for eight months after implantation are reported., At baseline the patient had daily absence seizures, 5 drop attacks/week and one generalized tonic-clonic convulsion (GTC)/week. She has cognitive impairment with limited speech, but has remained independent in her activities of daily life. Microelectrode recording defined the superior and inferior boundaries of the ANT at surgery. Unit activity within the target correlated with the patient[apos]s level of alertness (figure).
Stimulation was initiated at 160 Hs, 1 min ON, 5 min OFF with an 1V increase every 2h up to 5V. Prolonged EEG did not indicate any significant changes in the amount of epileptiform activity (EA)(p[gt]0.05) with increased voltage.
For two months the patient had a dramatic clinical response with only 2 drop attacks/month and one GTC/month. Alertness and school performance improved significantly. Continuous stimulation at 5V was started after two months. Three months after implantation seizure frequency increased slowly to 2 drop attacks/ week, frequent absences and occasional GTCs. Reverting to intermittent stimulation did not result in better seizure control.
Overall duration of EA during the awake state did not significantly change pre- or postimplant or related to stimulation parameters (23-33% preimplant, 16-47% postimplant, p=0.53). There was a trend towards EA becoming more fragmented and shorter in burst duration, but this did not reach statistical signficance (p=0.12). Background activity was better formed with DBS. The amount of EA was independent of continuous versus intermittent stimulation (p=0.53)., DBS can improve seizure frequency in the treatment of epileptic encephalopathy. The amount of epileptiform activity does not appear to be affected by thalamic stimulation. Results need to be validated in larger studies.[figure1],